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A San Diego prosecutor revealed the extremely graphic, violent details Friday of two separate assaults on two women allegedly committed by a man who met his victims through online escort ads and tortured them in ways deemed “unimaginable” by the prosecutor.

“This case is horrific. It is actually unimaginable, but it happened,” said San Diego Deputy District Attorney Mary Ellen Barrett, referring to a case involving 31-year-old suspect Brendan Mathis. “It’s frightening.”

Mathis was arrested Wednesday at a Mission Valley apartment complex on Fenton Parkway. San Diego police said Mathis went to the complex to meet with a paid escort he connected with through an online ad. When he arrived at the woman’s apartment, he allegedly attacked her with a taser and tried to tie her up.

On Thursday, Lt. Chuck Kaye with the San Diego Police Department Sex Crimes Unit told NBC 7 that Mathis' victim was a paid escort. Lt. Kaye also said Mathis had attacked another escort in a similar manner earlier this month.

After Mathis’ arraignment Friday, where he pleaded not guilty to all charges, Barrett laid out the sordid details of the alleged attack on that first victim, which occurred on Jan. 10 in a hotel room in Mission Valley.

According to the prosecutor, Mathis also met that victim through an online ad. When he arrived at the woman’s hotel room he allegedly tased her, attacked her and forced her to the ground.

Man Brought Hatchet, Taser to Escort's Apt: Cops

“He bound her hands and feet and said that he had an axe and he was going to kill her, and that she should just go along and cooperate,” Barrett explained. “He told her not to scream.”

Barrett alleged that Mathis then proceeded to blindfold his victim. At one point he allegedly flicked the burning amber from a cigarette at the woman’s private parts.

After that, Barrett said the woman was subjected to a “four or five-hour-long” torture session that included repeated, forced oral copulation so violent that Barrett said the victim suffered injuries. The prosecutor said the alleged attacker would take short breaks between the forced oral sex acts.

He then allegedly raped the woman.

Barrett said Mathis eventually took off the victim’s blindfold. Able to see again, the woman then spotted an axe lying close to her. Barrett said the woman also allegedly saw “other tools laid out” in the room, including garden shears, a knife and zip ties.

At the end of the lengthy assault, Barrett said Mathis forced the woman into the bathtub and told her to take a shower. He then told her to stay in the bathroom until an alarm went off and walked out of the room, laughing, according to the prosecutor.

Barrett said Mathis’ assault on the second victim this week was “very similar” in nature to the first attack -- only this time, the woman escaped.

Barrett said the suspect tied that victim’s hands behind her back and threatened to kill her.

The woman was able to make her way to a sliding glass door that led to her balcony and that’s when she jumped from the second-story, Barrett said, falling onto an air-conditioning unit below. The woman ran for help and shortly thereafter, police arrested Mathis near the apartment complex.

Barrett said Mathis gave investigators a statement in which he admitted guilt on both cases.

Though his motive for the alleged attacks remains under investigation, Barrett said the suspect told investigators he had a dark side.

“He said something came over him and it is dark,” she explained.

The prosecutor also said Mathis admitted he “targeted these women for their vulnerability.”

Barrett said Mathis faces a total of at least eight counts for the attacks on the two victims, including charges of torture, assault and rape. If convicted, he faces multiple life terms in prison.

Although police have said Mathis’ victims were both paid escorts, Barrett said this does not matter.

“A victim is a victim, regardless of what they were doing,” she added. “Anything we can do to protect the victims and to see that they’re protected in the future and that justice is done is what we’re going to have to do.”

At this point, Barrett said she’s not sure if there are more victims of Mathis’ alleged crimes but said she wouldn’t be surprised if there are more victims out there. She said any additional victims should come forward and contact the San Diego Police Department.

In court before a judge Friday, Mathis looked down and remained mostly quiet. He pleaded not guilty to the charges.

When a judge ordered him to stay away from his victims he briefly replied: “Yes, sir."

Mathis is currently being held on $4 million bail at San Diego Central Jail. He's scheduled to appear in court again on Feb. 11.